/*
 * Copyright 2018 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/core/SkGlyph.h"

#include "include/core/SkCanvas.h"
#include "include/core/SkData.h"
#include "include/core/SkDrawable.h"
#include "include/core/SkPicture.h"
#include "include/core/SkScalar.h"
#include "include/core/SkSerialProcs.h"
#include "include/core/SkSpan.h"
#include "include/private/base/SkFloatingPoint.h"
#include "include/private/base/SkTFitsIn.h"
#include "include/private/base/SkTo.h"
#include "src/base/SkArenaAlloc.h"
#include "src/base/SkBezierCurves.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkScalerContext.h"
#include "src/core/SkWriteBuffer.h"
#include "src/text/StrikeForGPU.h"

#include <cstring>
#include <optional>
#include <tuple>
#include <utility>

using namespace skglyph;
using namespace sktext;

// -- SkPictureBackedGlyphDrawable -----------------------------------------------------------------
sk_sp<SkPictureBackedGlyphDrawable> SkPictureBackedGlyphDrawable::MakeFromBuffer(SkReadBuffer &buffer)
{
    SkASSERT(buffer.isValid());

    sk_sp<SkData> pictureData = buffer.readByteArrayAsData();

    // Return nullptr if invalid or there an empty drawable, which is represented by nullptr.
    if (!buffer.isValid() || pictureData->size() == 0) {
        return nullptr;
    }

    // Propagate the outer buffer's allow-SkSL setting to the picture decoder, using the flag on
    // the deserial procs.
    SkDeserialProcs procs;
    procs.fAllowSkSL = buffer.allowSkSL();
    sk_sp<SkPicture> picture = SkPicture::MakeFromData(pictureData.get(), &procs);
    if (!buffer.validate(picture != nullptr)) {
        return nullptr;
    }

    return sk_make_sp<SkPictureBackedGlyphDrawable>(std::move(picture));
}

void SkPictureBackedGlyphDrawable::FlattenDrawable(SkWriteBuffer &buffer, SkDrawable *drawable)
{
    if (drawable == nullptr) {
        buffer.writeByteArray(nullptr, 0);
        return;
    }

    sk_sp<SkPicture> picture = drawable->makePictureSnapshot();
    // These drawables should not have SkImages, SkTypefaces or SkPictures inside of them, so
    // the default SkSerialProcs are sufficient.
    sk_sp<SkData> data = picture->serialize();

    // If the picture is too big, or there is no picture, then drop by sending an empty byte array.
    if (!SkTFitsIn<uint32_t>(data->size()) || data->size() == 0) {
        buffer.writeByteArray(nullptr, 0);
        return;
    }

    buffer.writeByteArray(data->data(), data->size());
}

SkPictureBackedGlyphDrawable::SkPictureBackedGlyphDrawable(sk_sp<SkPicture> picture) : fPicture(std::move(picture)) {}

SkRect SkPictureBackedGlyphDrawable::onGetBounds()
{
    return fPicture->cullRect();
}

size_t SkPictureBackedGlyphDrawable::onApproximateBytesUsed()
{
    return sizeof(SkPictureBackedGlyphDrawable) + fPicture->approximateBytesUsed();
}

void SkPictureBackedGlyphDrawable::onDraw(SkCanvas *canvas)
{
    canvas->drawPicture(fPicture);
}

// -- SkGlyph ---------------------------------------------------------------------------------------
std::optional<SkGlyph> SkGlyph::MakeFromBuffer(SkReadBuffer &buffer)
{
    SkASSERT(buffer.isValid());
    const SkPackedGlyphID packedID{ buffer.readUInt() };
    const SkVector advance = buffer.readPoint();
    const uint32_t dimensions = buffer.readUInt();
    const uint32_t leftTop = buffer.readUInt();
    const SkMask::Format format = SkTo<SkMask::Format>(buffer.readUInt());

    if (!buffer.validate(SkMask::IsValidFormat(format))) {
        return std::nullopt;
    }

    SkGlyph glyph{ packedID };
    glyph.fAdvanceX = advance.x();
    glyph.fAdvanceY = advance.y();
    glyph.fWidth = dimensions >> 16;
    glyph.fHeight = dimensions & 0xffffu;
    glyph.fLeft = leftTop >> 16;
    glyph.fTop = leftTop & 0xffffu;
    glyph.fMaskFormat = format;
    SkDEBUGCODE(glyph.fAdvancesBoundsFormatAndInitialPathDone = true;) return glyph;
}

SkGlyph::SkGlyph(const SkGlyph &) = default;
SkGlyph &SkGlyph::operator = (const SkGlyph &) = default;
SkGlyph::SkGlyph(SkGlyph &&) = default;
SkGlyph &SkGlyph::operator = (SkGlyph &&) = default;
SkGlyph::~SkGlyph() = default;

SkMask SkGlyph::mask() const
{
    SkIRect bounds = SkIRect::MakeXYWH(fLeft, fTop, fWidth, fHeight);
    return SkMask(static_cast<const uint8_t *>(fImage), bounds, this->rowBytes(), fMaskFormat);
}

SkMask SkGlyph::mask(SkPoint position) const
{
    SkASSERT(SkScalarIsInt(position.x()) && SkScalarIsInt(position.y()));
    SkIRect bounds = SkIRect::MakeXYWH(fLeft, fTop, fWidth, fHeight);
    bounds.offset(SkScalarFloorToInt(position.x()), SkScalarFloorToInt(position.y()));
    return SkMask(static_cast<const uint8_t *>(fImage), bounds, this->rowBytes(), fMaskFormat);
}

void SkGlyph::zeroMetrics()
{
    fAdvanceX = 0;
    fAdvanceY = 0;
    fWidth = 0;
    fHeight = 0;
    fTop = 0;
    fLeft = 0;
}

static size_t bits_to_bytes(size_t bits)
{
    return (bits + 7) >> 3;
}

static size_t format_alignment(SkMask::Format format)
{
    switch (format) {
        case SkMask::kBW_Format:
        case SkMask::kA8_Format:
        case SkMask::k3D_Format:
        case SkMask::kSDF_Format:
            return alignof(uint8_t);
        case SkMask::kARGB32_Format:
            return alignof(uint32_t);
        case SkMask::kLCD16_Format:
            return alignof(uint16_t);
        default:
            SK_ABORT("Unknown mask format.");
            break;
    }
    return 0;
}

static size_t format_rowbytes(int width, SkMask::Format format)
{
    return format == SkMask::kBW_Format ? bits_to_bytes(width) : width * format_alignment(format);
}

size_t SkGlyph::formatAlignment() const
{
    return format_alignment(this->maskFormat());
}

size_t SkGlyph::allocImage(SkArenaAlloc *alloc)
{
    SkASSERT(!this->isEmpty());
    auto size = this->imageSize();
    fImage = alloc->makeBytesAlignedTo(size, this->formatAlignment());

    return size;
}

bool SkGlyph::setImage(SkArenaAlloc *alloc, SkScalerContext *scalerContext)
{
    if (!this->setImageHasBeenCalled()) {
        // It used to be that getImage() could change the fMaskFormat. Extra checking to make
        // sure there are no regressions.
        SkDEBUGCODE(SkMask::Format oldFormat = this->maskFormat());
        this->allocImage(alloc);
        scalerContext->getImage(*this);
        SkASSERT(oldFormat == this->maskFormat());
        return true;
    }
    return false;
}

bool SkGlyph::setImage(SkArenaAlloc *alloc, const void *image)
{
    if (!this->setImageHasBeenCalled()) {
        this->allocImage(alloc);
        memcpy(fImage, image, this->imageSize());
        return true;
    }
    return false;
}

size_t SkGlyph::setMetricsAndImage(SkArenaAlloc *alloc, const SkGlyph &from)
{
    // Since the code no longer tries to find replacement glyphs, the image should always be
    // nullptr.
    SkASSERT(fImage == nullptr || from.fImage == nullptr);

    // TODO(herb): remove "if" when we are sure there are no colliding glyphs.
    if (fImage == nullptr) {
        fAdvanceX = from.fAdvanceX;
        fAdvanceY = from.fAdvanceY;
        fWidth = from.fWidth;
        fHeight = from.fHeight;
        fTop = from.fTop;
        fLeft = from.fLeft;
        fScalerContextBits = from.fScalerContextBits;
        fMaskFormat = from.fMaskFormat;

        // From glyph may not have an image because the glyph is too large.
        if (from.fImage != nullptr && this->setImage(alloc, from.image())) {
            return this->imageSize();
        }

        SkDEBUGCODE(fAdvancesBoundsFormatAndInitialPathDone = from.fAdvancesBoundsFormatAndInitialPathDone;)
    }
    return 0;
}

size_t SkGlyph::rowBytes() const
{
    return format_rowbytes(fWidth, fMaskFormat);
}

size_t SkGlyph::rowBytesUsingFormat(SkMask::Format format) const
{
    return format_rowbytes(fWidth, format);
}

size_t SkGlyph::imageSize() const
{
    if (this->isEmpty() || this->imageTooLarge()) {
        return 0;
    }

    size_t size = this->rowBytes() * fHeight;

    if (fMaskFormat == SkMask::k3D_Format) {
        size *= 3;
    }

    return size;
}

void SkGlyph::installPath(SkArenaAlloc *alloc, const SkPath *path, bool hairline)
{
    SkASSERT(fPathData == nullptr);
    SkASSERT(!this->setPathHasBeenCalled());
    fPathData = alloc->make<SkGlyph::PathData>();
    if (path != nullptr) {
        fPathData->fPath = *path;
        fPathData->fPath.updateBoundsCache();
        fPathData->fPath.getGenerationID();
        fPathData->fHasPath = true;
        fPathData->fHairline = hairline;
    }
}

bool SkGlyph::setPath(SkArenaAlloc *alloc, SkScalerContext *scalerContext)
{
    if (!this->setPathHasBeenCalled()) {
        scalerContext->getPath(*this, alloc);
        SkASSERT(this->setPathHasBeenCalled());
        return this->path() != nullptr;
    }

    return false;
}

bool SkGlyph::setPath(SkArenaAlloc *alloc, const SkPath *path, bool hairline)
{
    if (!this->setPathHasBeenCalled()) {
        this->installPath(alloc, path, hairline);
        return this->path() != nullptr;
    }
    return false;
}

const SkPath *SkGlyph::path() const
{
    // setPath must have been called previously.
    SkASSERT(this->setPathHasBeenCalled());
    if (fPathData->fHasPath) {
        return &fPathData->fPath;
    }
    return nullptr;
}

bool SkGlyph::pathIsHairline() const
{
    // setPath must have been called previously.
    SkASSERT(this->setPathHasBeenCalled());
    return fPathData->fHairline;
}

void SkGlyph::installDrawable(SkArenaAlloc *alloc, sk_sp<SkDrawable> drawable)
{
    SkASSERT(fDrawableData == nullptr);
    SkASSERT(!this->setDrawableHasBeenCalled());
    fDrawableData = alloc->make<SkGlyph::DrawableData>();
    if (drawable != nullptr) {
        fDrawableData->fDrawable = std::move(drawable);
        fDrawableData->fDrawable->getGenerationID();
        fDrawableData->fHasDrawable = true;
    }
}

bool SkGlyph::setDrawable(SkArenaAlloc *alloc, SkScalerContext *scalerContext)
{
    if (!this->setDrawableHasBeenCalled()) {
        sk_sp<SkDrawable> drawable = scalerContext->getDrawable(*this);
        this->installDrawable(alloc, std::move(drawable));
        return this->drawable() != nullptr;
    }
    return false;
}

bool SkGlyph::setDrawable(SkArenaAlloc *alloc, sk_sp<SkDrawable> drawable)
{
    if (!this->setDrawableHasBeenCalled()) {
        this->installDrawable(alloc, std::move(drawable));
        return this->drawable() != nullptr;
    }
    return false;
}

SkDrawable *SkGlyph::drawable() const
{
    // setDrawable must have been called previously.
    SkASSERT(this->setDrawableHasBeenCalled());
    if (fDrawableData->fHasDrawable) {
        return fDrawableData->fDrawable.get();
    }
    return nullptr;
}

void SkGlyph::flattenMetrics(SkWriteBuffer &buffer) const
{
    buffer.writeUInt(fID.value());
    buffer.writePoint({ fAdvanceX, fAdvanceY });
    buffer.writeUInt(fWidth << 16 | fHeight);
    // Note: << has undefined behavior for negative values, so convert everything to the bit
    // values of uint16_t. Using the cast keeps the signed values fLeft and fTop from sign
    // extending.
    const uint32_t left = static_cast<uint16_t>(fLeft);
    const uint32_t top = static_cast<uint16_t>(fTop);
    buffer.writeUInt(left << 16 | top);
    buffer.writeUInt(SkTo<uint32_t>(fMaskFormat));
}

void SkGlyph::flattenImage(SkWriteBuffer &buffer) const
{
    SkASSERT(this->setImageHasBeenCalled());

    // If the glyph is empty or too big, then no image data is sent.
    if (!this->isEmpty() && SkGlyphDigest::FitsInAtlas(*this)) {
        buffer.writeByteArray(this->image(), this->imageSize());
    }
}

size_t SkGlyph::addImageFromBuffer(SkReadBuffer &buffer, SkArenaAlloc *alloc)
{
    SkASSERT(buffer.isValid());

    // If the glyph is empty or too big, then no image data is received.
    if (this->isEmpty() || !SkGlyphDigest::FitsInAtlas(*this)) {
        return 0;
    }

    size_t memoryIncrease = 0;

    void *imageData = alloc->makeBytesAlignedTo(this->imageSize(), this->formatAlignment());
    buffer.readByteArray(imageData, this->imageSize());
    if (buffer.isValid()) {
        this->installImage(imageData);
        memoryIncrease += this->imageSize();
    }

    return memoryIncrease;
}

void SkGlyph::flattenPath(SkWriteBuffer &buffer) const
{
    SkASSERT(this->setPathHasBeenCalled());

    const bool hasPath = this->path() != nullptr;
    buffer.writeBool(hasPath);
    if (hasPath) {
        buffer.writeBool(this->pathIsHairline());
        buffer.writePath(*this->path());
    }
}

size_t SkGlyph::addPathFromBuffer(SkReadBuffer &buffer, SkArenaAlloc *alloc)
{
    SkASSERT(buffer.isValid());

    size_t memoryIncrease = 0;
    const bool hasPath = buffer.readBool();
    // Check if the buffer is invalid, so as to not make a logical decision on invalid data.
    if (!buffer.isValid()) {
        return 0;
    }
    if (hasPath) {
        const bool pathIsHairline = buffer.readBool();
        SkPath path;
        buffer.readPath(&path);
        if (buffer.isValid()) {
            if (this->setPath(alloc, &path, pathIsHairline)) {
                memoryIncrease += path.approximateBytesUsed();
            }
        }
    } else {
        this->setPath(alloc, nullptr, false);
    }

    return memoryIncrease;
}

void SkGlyph::flattenDrawable(SkWriteBuffer &buffer) const
{
    SkASSERT(this->setDrawableHasBeenCalled());

    if (this->isEmpty() || this->drawable() == nullptr) {
        SkPictureBackedGlyphDrawable::FlattenDrawable(buffer, nullptr);
        return;
    }

    SkPictureBackedGlyphDrawable::FlattenDrawable(buffer, this->drawable());
}

size_t SkGlyph::addDrawableFromBuffer(SkReadBuffer &buffer, SkArenaAlloc *alloc)
{
    SkASSERT(buffer.isValid());

    sk_sp<SkDrawable> drawable = SkPictureBackedGlyphDrawable::MakeFromBuffer(buffer);
    if (!buffer.isValid()) {
        return 0;
    }

    if (this->setDrawable(alloc, std::move(drawable))) {
        return this->drawable()->approximateBytesUsed();
    }

    return 0;
}

static std::tuple<SkScalar, SkScalar> calculate_path_gap(SkScalar topOffset, SkScalar bottomOffset, const SkPath &path)
{
    // Left and Right of an ever expanding gap around the path.
    SkScalar left = SK_ScalarMax, right = SK_ScalarMin;

    auto expandGap = [&left, &right](SkScalar v) {
        left = std::min(left, v);
        right = std::max(right, v);
    };

    // Handle all the different verbs for the path.
    SkPoint pts[4];
    auto addLine = [&](SkScalar offset) {
        SkScalar t = sk_ieee_float_divide(offset - pts[0].fY, pts[1].fY - pts[0].fY);
        if (0 <= t && t < 1) { // this handles divide by zero above
            expandGap(pts[0].fX + t * (pts[1].fX - pts[0].fX));
        }
    };

    auto addQuad = [&](SkScalar offset) {
        SkScalar intersectionStorage[2];
        auto intersections = SkBezierQuad::IntersectWithHorizontalLine(SkSpan(pts, 3), offset, intersectionStorage);
        for (SkScalar x : intersections) {
            expandGap(x);
        }
    };

    auto addCubic = [&](SkScalar offset) {
        float intersectionStorage[3];
        auto intersections = SkBezierCubic::IntersectWithHorizontalLine(SkSpan{ pts, 4 }, offset, intersectionStorage);

        for (double intersection : intersections) {
            expandGap(intersection);
        }
    };

    // Handle when a verb's points are in the gap between top and bottom.
    auto addPts = [&expandGap, &pts, topOffset, bottomOffset](int ptCount) {
        for (int i = 0; i < ptCount; ++i) {
            if (topOffset < pts[i].fY && pts[i].fY < bottomOffset) {
                expandGap(pts[i].fX);
            }
        }
    };

    SkPath::Iter iter(path, false);
    SkPath::Verb verb;
    while (SkPath::kDone_Verb != (verb = iter.next(pts))) {
        switch (verb) {
            case SkPath::kMove_Verb: {
                break;
            }
            case SkPath::kLine_Verb: {
                auto [lineTop, lineBottom] = std::minmax({ pts[0].fY, pts[1].fY });

                // The y-coordinates of the points intersect the top and bottom offsets.
                if (topOffset <= lineBottom && lineTop <= bottomOffset) {
                    addLine(topOffset);
                    addLine(bottomOffset);
                    addPts(2);
                }
                break;
            }
            case SkPath::kQuad_Verb: {
                auto [quadTop, quadBottom] = std::minmax({ pts[0].fY, pts[1].fY, pts[2].fY });

                // The y-coordinates of the points intersect the top and bottom offsets.
                if (topOffset <= quadBottom && quadTop <= bottomOffset) {
                    addQuad(topOffset);
                    addQuad(bottomOffset);
                    addPts(3);
                }
                break;
            }
            case SkPath::kConic_Verb: {
                SkDEBUGFAIL("There should be no conic primitives in glyph outlines.");
                break;
            }
            case SkPath::kCubic_Verb: {
                auto [cubicTop, cubicBottom] = std::minmax({ pts[0].fY, pts[1].fY, pts[2].fY, pts[3].fY });

                // The y-coordinates of the points intersect the top and bottom offsets.
                if (topOffset <= cubicBottom && cubicTop <= bottomOffset) {
                    addCubic(topOffset);
                    addCubic(bottomOffset);
                    addPts(4);
                }
                break;
            }
            case SkPath::kClose_Verb: {
                break;
            }
            default: {
                SkDEBUGFAIL("Unknown path verb generating glyph underline.");
                break;
            }
        }
    }

    return std::tie(left, right);
}

void SkGlyph::ensureIntercepts(const SkScalar *bounds, SkScalar scale, SkScalar xPos, SkScalar *array, int *count,
    SkArenaAlloc *alloc)
{
    auto offsetResults = [scale, xPos](const SkGlyph::Intercept *intercept, SkScalar *array, int *count) {
        if (array) {
            array += *count;
            for (int index = 0; index < 2; index++) {
                *array++ = intercept->fInterval[index] * scale + xPos;
            }
        }
        *count += 2;
    };

    const SkGlyph::Intercept *match = [this](const SkScalar bounds[2]) -> const SkGlyph::Intercept * {
        if (fPathData == nullptr) {
            return nullptr;
        }
        const SkGlyph::Intercept *intercept = fPathData->fIntercept;
        while (intercept != nullptr) {
            if (bounds[0] == intercept->fBounds[0] && bounds[1] == intercept->fBounds[1]) {
                return intercept;
            }
            intercept = intercept->fNext;
        }
        return nullptr;
    }(bounds);

    if (match != nullptr) {
        if (match->fInterval[0] < match->fInterval[1]) {
            offsetResults(match, array, count);
        }
        return;
    }

    SkGlyph::Intercept *intercept = alloc->make<SkGlyph::Intercept>();
    intercept->fNext = fPathData->fIntercept;
    intercept->fBounds[0] = bounds[0];
    intercept->fBounds[1] = bounds[1];
    intercept->fInterval[0] = SK_ScalarMax;
    intercept->fInterval[1] = SK_ScalarMin;
    fPathData->fIntercept = intercept;
    const SkPath *path = &(fPathData->fPath);
    const SkRect &pathBounds = path->getBounds();
    if (pathBounds.fBottom < bounds[0] || bounds[1] < pathBounds.fTop) {
        return;
    }

    std::tie(intercept->fInterval[0], intercept->fInterval[1]) = calculate_path_gap(bounds[0], bounds[1], *path);

    if (intercept->fInterval[0] >= intercept->fInterval[1]) {
        intercept->fInterval[0] = SK_ScalarMax;
        intercept->fInterval[1] = SK_ScalarMin;
        return;
    }
    offsetResults(intercept, array, count);
}

namespace {
uint32_t init_actions(const SkGlyph &glyph)
{
    constexpr uint32_t kAllUnset = 0;
    constexpr uint32_t kDrop = SkTo<uint32_t>(GlyphAction::kDrop);
    constexpr uint32_t kAllDrop = kDrop << kDirectMask | kDrop << kDirectMaskCPU | kDrop << kMask | kDrop << kSDFT |
        kDrop << kPath | kDrop << kDrawable;
    return glyph.isEmpty() ? kAllDrop : kAllUnset;
}
} // namespace

// -- SkGlyphDigest --------------------------------------------------------------------------------
SkGlyphDigest::SkGlyphDigest(size_t index, const SkGlyph &glyph)
    : fPackedID{ SkTo<uint64_t>(glyph.getPackedID().value()) },
      fIndex{ SkTo<uint64_t>(index) },
      fIsEmpty(glyph.isEmpty()),
      fFormat(glyph.maskFormat()),
      fActions{ init_actions(glyph) },
      fLeft{ SkTo<int16_t>(glyph.left()) },
      fTop{ SkTo<int16_t>(glyph.top()) },
      fWidth{ SkTo<uint16_t>(glyph.width()) },
      fHeight{ SkTo<uint16_t>(glyph.height()) }
{}

void SkGlyphDigest::setActionFor(skglyph::ActionType actionType, SkGlyph *glyph, StrikeForGPU *strike)
{
    // We don't have to do any more if the glyph is marked as kDrop because it was isEmpty().
    if (this->actionFor(actionType) == GlyphAction::kUnset) {
        GlyphAction action = GlyphAction::kReject;
        switch (actionType) {
            case kDirectMask: {
                if (this->fitsInAtlasDirect()) {
                    action = GlyphAction::kAccept;
                }
                break;
            }
            case kDirectMaskCPU: {
                if (strike->prepareForImage(glyph)) {
                    SkASSERT(!glyph->isEmpty());
                    action = GlyphAction::kAccept;
                }
                break;
            }
            case kMask: {
                if (this->fitsInAtlasInterpolated()) {
                    action = GlyphAction::kAccept;
                }
                break;
            }
            case kSDFT: {
                if (this->fitsInAtlasDirect() && this->maskFormat() == SkMask::Format::kSDF_Format) {
                    action = GlyphAction::kAccept;
                }
                break;
            }
            case kPath: {
                if (strike->prepareForPath(glyph)) {
                    action = GlyphAction::kAccept;
                }
                break;
            }
            case kDrawable: {
                if (strike->prepareForDrawable(glyph)) {
                    action = GlyphAction::kAccept;
                }
                break;
            }
        }
        this->setAction(actionType, action);
    }
}

bool SkGlyphDigest::FitsInAtlas(const SkGlyph &glyph)
{
    return glyph.maxDimension() <= kSkSideTooBigForAtlas;
}

// -- SkGlyphPositionRoundingSpec ------------------------------------------------------------------
SkVector SkGlyphPositionRoundingSpec::HalfAxisSampleFreq(bool isSubpixel, SkAxisAlignment axisAlignment)
{
    if (!isSubpixel) {
        return { SK_ScalarHalf, SK_ScalarHalf };
    } else {
        switch (axisAlignment) {
            case SkAxisAlignment::kX:
                return { SkPackedGlyphID::kSubpixelRound, SK_ScalarHalf };
            case SkAxisAlignment::kY:
                return { SK_ScalarHalf, SkPackedGlyphID::kSubpixelRound };
            case SkAxisAlignment::kNone:
                return { SkPackedGlyphID::kSubpixelRound, SkPackedGlyphID::kSubpixelRound };
        }
    }

    // Some compilers need this.
    return { 0, 0 };
}

SkIPoint SkGlyphPositionRoundingSpec::IgnorePositionMask(bool isSubpixel, SkAxisAlignment axisAlignment)
{
    return SkIPoint::Make((!isSubpixel || axisAlignment == SkAxisAlignment::kY) ? 0 : ~0,
        (!isSubpixel || axisAlignment == SkAxisAlignment::kX) ? 0 : ~0);
}

SkIPoint SkGlyphPositionRoundingSpec::IgnorePositionFieldMask(bool isSubpixel, SkAxisAlignment axisAlignment)
{
    SkIPoint ignoreMask = IgnorePositionMask(isSubpixel, axisAlignment);
    SkIPoint answer{ ignoreMask.x() & SkPackedGlyphID::kXYFieldMask.x(),
        ignoreMask.y() & SkPackedGlyphID::kXYFieldMask.y() };
    return answer;
}

SkGlyphPositionRoundingSpec::SkGlyphPositionRoundingSpec(bool isSubpixel, SkAxisAlignment axisAlignment)
    : halfAxisSampleFreq{ HalfAxisSampleFreq(isSubpixel, axisAlignment) },
      ignorePositionMask{ IgnorePositionMask(isSubpixel, axisAlignment) },
      ignorePositionFieldMask{ IgnorePositionFieldMask(isSubpixel, axisAlignment) }
{}
